Vessel filter

ABSTRACT

A method of removing an implanted vessel filter by a femoral approach comprising the steps of providing a catheter with a curved tip, inserting a straightening device into the catheter to move the catheter tip from a curved position to a more straightened position, advancing the catheter tip through the femoral vein and past a cranial end of the filter, withdrawing the straightening device to enable the catheter tip to return to the curved condition, and inserting a filter grasping device though the catheter and a curved catheter tip to exit a distal portion to grasp the filter.

This application claims priority from provisional application Ser. No.60/818,202, filed Jun. 30, 2006, and is a continuation-in-part ofapplication Ser. No. 10/899,429, filed Jul. 12, 2004 which claimspriority from provisional application Ser. No. 60/572,274, filed May 18,2004, and is a continuation-in-part of application Ser. No. 10/805,796filed Mar. 22, 2004, which claims priority from provisional applicationSer. No. 60/538,379, filed Jan. 22, 2004. The entire contents of theseapplications are incorporated herein by reference.

BACKGROUND

1. Technical Field

This application relates to a vascular filter and more particularly to amethod of removing a vein filter from the vessel.

2. Background of Related Art

Passage of blood clots to the lungs is known as pulmonary embolism.These clots typically originate in the veins of the lower limbs and canmigrate through the vascular system to the lungs where they can obstructblood flow and therefore interfere with oxygenation of the blood.Pulmonary embolisms can also cause shock and even death.

In some instances, blood thinning medication, e.g. anticoagulants suchas Heparin, or sodium warfarin can be given to the patient. Thesemedications, however, have limited use since they may not be able to beadministered to patients after surgery or stroke or given to patientswith high risk of internal bleeding. Also, this medication approach isnot always effective in preventing recurring blood clots.

To avoid invasive surgery, less invasive surgical techniques involvingplacement of a mechanical barrier in the inferior vena cava have beendeveloped. These barriers are in the form of filters and are typicallyinserted through either the femoral vein in the patient's leg or theright jugular vein in the patient's neck or arm under local anesthesia.The filters are then advanced intravascularly to the inferior vena cavawhere they are expanded to block migration of the blood clots from thelower portion of the body to the heart and lungs.

These prior filters take various forms. One type of filter is composedof coiled wires such as disclosed in U.S. Pat. Nos. 5,893,869 and6,059,825. Another type of filter consists of legs with free ends havinganchors for embedding in the vessel wall to hold the filter. Thesefilters are disclosed, for example, in U.S. Pat. Nos. 4,688,553,4,781,173, 4,832,055, and 5,059,205, 5,984,947 and 6,007,558. Anothertype of filter is disclosed in U.S. Pat. No. 6,214,025 consisting ofwires twisted together to form a cylindrical anchoring portionconforming to the inner vessel wall surface to exert a radial force anda conical filtering portion.

Co-pending commonly assigned U.S. application Ser. No. 10/899,429 (the“'429 application”), the entire contents of which is incorporated hereinby reference, discloses other forms of vein filters. These filters canbe permanently implanted or removed minimally invasively, e.g.intravascularly. The '429 application discloses various configurationsof the cranial end of the filter to facilitate removal. The filters ofthe '429 application are generally designed to be removed from a jugularapproach since the retrieval hook portion is located on the cranial end.It would be advantageous to provide a method for retrieving thesefilters utilizing a femoral approach as well. Such femoral approachcould advantageously also be utilized to retrieve other filters.

SUMMARY

The present invention provides a method of removing an implanted vesselfilter by a femoral approach comprising the steps of: providing acatheter with a curved tip; inserting a straightening device into thecatheter to move the catheter tip from a curved position to a morestraightened position; advancing the catheter tip through the femoralvein and past a cranial end of the implanted filter; withdrawing thestraightening device to enable the catheter tip to return to the curvedposition; and inserting a filter grasping device through the catheterand curved catheter tip to exit a distal portion to grasp the filter.

The step of inserting the filter grasping device preferably includes thestep of inserting a snare to engage a hook portion at the cranial end ofthe filter. Preferably the method includes the step of pulling thefilter into a lumen of the catheter after grasping of the filter. Thestep of advancing the catheter tip preferably includes the step ofadvancing the catheter and straightening device over a guidewire.Subsequent to the step of withdrawing the filter, the catheter tip ispreferably moved to a more straightened position to facilitate removalof the catheter. The method steps may also include advancing thecatheter after grasping the filter to disengage filter hooks from thevessel wall.

The present invention also provides a method of removing an implantedvessel filter by a femoral approach comprising the steps of providing acatheter with a tip; inserting a curved device into the catheter to aposition proximal of the tip; advancing the catheter tip through thefemoral vein and past a cranial end of the implanted filter; insertingthe curved device into the catheter tip to move the catheter tip from afirst more straightened position to a second more curved position; andinserting a filter grasping device though the curved device, catheterand curved catheter tip to exit a distal portion to grasp the filter.

The step of inserting the filter grasping device may include the step ofinserting a snare to engage the filter. The catheter may have a firsthardness at an intermediate portion and a second hardness less than thefirst hardness at the tip such that in the step of inserting the curveddevice, the first hardness maintains the curved device in a morestraightened position and the second hardness allows the curved deviceto move to a more curved position to thereby move the catheter tip tothe more curved position.

The method may further include the step of pulling the filter into alumen of the curved device after grasping of the filter.

The method may further comprise the step of withdrawing the filter andgrasping device through the catheter, wherein subsequent to the step ofwithdrawing the filter, the method includes the step of withdrawing thecurved device from the catheter tip to move the catheter tip to a morestraightened position.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiment(s) of the present disclosure are described hereinwith reference to the drawings wherein:

FIG. 1 is a broken perspective view of the retrieval catheter with adilator positioned therein to straighten the catheter tip;

FIG. 2 is a broken perspective view of the catheter of FIG. 1 with thedilator removed and the catheter tip in the curved position;

FIGS. 3-14 illustrate the method steps of the present invention forretrieving a filter by a femoral approach, wherein

FIG. 3 illustrates initial insertion of the guidewire through thefemoral vein;

FIG. 4 illustrates the retrieval catheter being advanced over aguidewire toward the inferior vena cava just below (upstream) thejuncture of the renal arteries to where the filter has been implanted;

FIG. 5 illustrates the tip of the retrieval catheter being advancedbeyond the implanted filter with the dilator still positioned in thecatheter to maintain the catheter tip in the straightened position;

FIG. 6 illustrates the dilator being withdrawn to enable the cathetertip to return to its normally curved position;

FIG. 7 illustrates a filter retrieval snare being inserted into theretrieval catheter;

FIG. 8 illustrates the filter retrieval snare advanced through theretrieval catheter, the snare shown exiting the distal tip of thecatheter and engaging the cranial end of the filter;

FIG. 9 is a close up view of the area of detail of FIG. 8 showing thesnare engaging the retrieval hook at the cranial end of the filter;

FIG. 10 is a close up view similar to FIG. 9 except showing the snaretightened around the retrieval hook of the filter;

FIG. 11 illustrates movement of the retrieval catheter distally todisengage the filter retention hooks from the vessel wall;

FIG. 11A illustrates an alternate embodiment to aid movement of theretrieval catheter distally by the use of a wire;

FIG. 12 illustrates retraction of the retrieval snare to remove thefilter from the vessel and pull it through the retrieval catheter;

FIG. 13 illustrates reinsertion of the dilator into the retrievalcatheter; and

FIG. 14 illustrates removal of the catheter after advancement of thedilator to the distal tip to straighten the tip.

FIG. 15A is a perspective view of one embodiment of a vein filter thatcan be removed using the retrieval catheter;

FIG. 15B is an enlarged developed view of the retention hooks of thefilter of FIG. 15A;

FIG. 16 is a perspective view of an alternate embodiment of a retrievalhook of a filter;

FIG. 17A is a broken perspective view of a retrieval catheter with astraight tip and showing a dilator being inserted therein;

FIG. 17B is a broken perspective view of the retrieval catheter of FIG.17A with the dilator fully inserted to move the catheter tip to thecurved position;

FIG. 18 is a perspective view of a cranial end of a filter have a domeshaped end; and

FIG. 19 is a perspective view of a cranial end of a filter having a domeshaped end with a notch formed therein.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Turning now to the drawings, wherein like reference numerals identifysimilar or like components throughout the several views, a method forretrieving vein filters utilizing a femoral approach is described. Inco-pending commonly assigned patent application Ser. No. 10/899,429,filed Jul. 12, 2004, various embodiments of filters are described withvarious structures, e.g. hooks, to facilitate removal. The '429application also describes retrieval of the filter through the catheter.Being that the retrieval structure of the filters is at the cranial end,the method of the present invention provides a way to retrieve thosefilters from the inferior vena cava, as well as other filters withretrieval hook or structure on the cranial end, utilizing a femoralapproach.

Turning initially to FIG. 1, the retrieval catheter or sheath 10 of thepresent invention has a body 12 and a distal tip 14. The distal tip 14has a curved shape as shown in FIG. 2 (the straightened shape is shownin phantom). The curved shape is the normal condition of the cathetertip 14 and the curve shown is about 180 degree turn although othercurves are also contemplated. The curved catheter tip 14 is sufficientlyflexible to be straightened by insertion of dilator 20 through lumen 16as shown in FIG. 1.

The retrieval method is illustrated by the method steps of FIGS. 3-14.After insertion of the guidewire 30 through the right femoral vein “f”(or alternatively the left), the guidewire 30 is maneuvered past thecranial end 54 of filter 50. Retrieval catheter 10, with dilator 20positioned therein, is then inserted through the femoral vein “f” andadvanced through the iliac veins into the inferior vena cava. (Tubing104 and valve assembly 106 enable saline injection described below.)That is, dilator 20 is positioned in the lumen 16 of the retrievalcatheter 10 during insertion to move and maintain the tip 14 in thesubstantially straightened position (or more straightened position) toenable advancement of the catheter through the vascular system.Retrieval catheter 10 and dilator 20 are inserted over guidewire 30 pastthe caudal end 52 of the filter 50 and beyond the cranial end 54 asshown in FIG. 5.

Dilator 20 (and guidewire 30) is then withdrawn as shown by the arrow inFIG. 6, which enables the distal tip 14 of catheter 10 to return to itsnormal more curved configuration. In this curved configuration, thedistal opening 18 of catheter 10 faces the cranial end of the filter andis maneuvered so opening 18 is above the hook 56 of filter 50. It couldalso be placed to substantially align with the hook.

Snare catheter 40 is inserted through the lumen 16 of the retrievalcatheter 10, as shown by the arrow of FIG. 7, and extends around thecurved distal tip 14 of catheter 10 as shown in FIGS. 8 and 9, exitingdistal opening 18.

The snare 42, movably positioned in a lumen of the snare catheter 40, isplaced around hook 56 of filter 50, and then tightened around the hookas shown in FIG. 10, by retraction of the snare wire to grasp thefilter. Once tightened, the catheter 10 is preferably moved distally(shown in phantom) in the direction of the arrow of FIG. 11 to disengagethe filter retention hooks 58 from the vessel wall. To facilitate suchdistal advancement and hook disengagement, a wire can be used as shownin the alternate embodiment of FIG. 11A. In this embodiment, catheter10′ has a side opening 15 through which wire 17 extends from thecatheter lumen, either the lumen for the snare or another lumen adjacentto the snare lumen. This stiffening wire 17 is pushed forward along withthe retrieval catheter 10′ to help move the catheter distally byproviding additional force on the catheter.

Once the filter retention hooks 58 are disengaged from the vessel wall,the snare catheter 40 is withdrawn, pulling the filter 50 into theretrieval catheter 10 as shown in FIG. 12. The snare catheter 40 andfilter 50 are then removed through the proximal end of the catheter 10.Next, the dilator 20, preferably with guidewire 30, is reinsertedthrough the catheter lumen 16 (FIG. 13) to straighten the distal tip 14(or move it to more straightened position). The retrieval catheter 10,with the straightened tip, along with the dilator 20 and guidewire 30,are then withdrawn from the body in the direction of the arrow of FIG.14.

FIGS. 17A and 17B illustrate an alternate retrieval catheter. Retrievalcatheter or sheath 110 has a substantially straight tip 114 and distalopening 118. The tip portion 115 of catheter 110 has a first hardnessand the intermediate portion 117 (or portion proximal of tip portion115) has a second hardness greater than the first hardness. A dilator orstylet 120 has a curved tip 122. The dilator 120 has a third hardnessgreater than the first hardness of the tip portion 115 but less than thesecond hardness of the intermediate portion 117. When the dilator 120 isinserted in the catheter 110 and the tip 122 is in the intermediateportion 117, the tip is restrained in a more straightened position dueto the greater hardness of portion 117. When the dilator 120 is furtherinserted so the tip 122 is in the tip portion 115, it is enabled toreturn to its normally curved position since its hardness is greaterthan that of tip portion 115, thereby forcing the distal tip 114 ofretrieval catheter 110 into a more curved position as shown in FIG. 17B.

Thus, in use, after insertion of the guidewire as described above,retrieval catheter 110, with dilator 120 positioned partially therein,is inserted through the femoral vein “f” and advanced through the iliacarteries into the inferior vena cava. Retrieval catheter 110 and dilator120 are inserted over the guidewire past the caudal end 52 of the filter50 and beyond the cranial end 54. (Alternatively, the dilator 120 can beinserted into catheter 110 after the catheter is inserted).

Dilator 120 is then fully inserted into the catheter 110 (and theguidewire withdrawn either prior to or after full insertion) to forcethe distal tip 114 of catheter 110 to its curved configuration. In thismore curved configuration, the distal opening 118 of catheter 110 facesthe cranial end of the filter and preferably is maneuvered so opening 18is above the hook 56 of filter 50.

Snare catheter 40 is inserted through the lumen of the dilator 120 andextends around curved tip 122 of dilator 120 and curved distal tip 114of catheter 110, exiting the distal opening of the dilator and thedistal opening 118 of the catheter 110.

The snare 42 is placed around hook 56 of filter 50, and then tightenedas described above. Once tightened, the catheter 10 is preferably moveddistally, also as described above, to disengage the filter retentionhooks 58 from the vessel wall. After the filter 50 is withdrawn, thedilator 120 is retracted to straighten the tip of catheter 110.

FIG. 15A shows an example of a filter that could be withdrawn using theretrieval method of the present invention. The filter 50 is shown in theexpanded placement configuration. It should be appreciated that otherfilters, including those described in the '429 application, could beretrieved using the femoral approach method described herein. The filter50 (and other filters described therein) can be inserted through thejugular vein in the neck of the patient or through the femoral vein inthe leg of the patient or the arm. The filters can also be placed in thesuperior vena cava.

Filter 50 is preferably made from a shape memory nitinol tube and has aflared region 57 and a converging region 51 at the filtering region 59.

Filtering region 59 has six struts 61 (only some of which are labeledfor clarity) curving outwardly from tubular portion 64. Each filterstrut or strut portion 61 extends radially from tubular portion 64 anddivides into two connecting filter struts or strut portions 61 a, 61 b(preferably of equal width) that angle way from each other (in differentdirections) to extend to the connecting strut portion of an adjacentstrut 61. After convergence of strut portions 61 a, 61 b at joiningregion 61 d, it transitions into elongated mounting strut portions 61 cwhich form flared mounting or anchoring region 57. The struts 61terminate in hooks 58, of two different sizes as described in the '429application. Hooks 58 include a series of teeth 58 a (FIG. 15B) toengage the vessel wall to provide additional retention to preventmovement of the implanted filter in the caudal direction. A heel 59extends past the hook to function as a stop to prevent the filter strutportions from going through the vessel wall.

The tubular portion 64 is preferably in the form of a retrieval hook asdescribed in the '429 application. Hook 56 has a curved hook 72 at theproximalmost end which is configured to receive a retrieval snare orother retrieval device. A portion of the wall of the hook 56 is cut outto expose the annular interior surface 74. The interior surface 74accommodates a portion of a tubular snare sheath. That is, the outerwall of the snare sheath (tube) can partially fit within the cut outregion. This enhances removal as the snare pulls the filter hook intocollinear arrangement with the sheath tube.

Engagement of the retrieval hook 56 and its retraction into the snaresheath or tube, including the collinear arrangement are described indetail and shown in FIGS. 13H-13N of the '429 application. When thefilter 50 is pulled into the retrieval sheath 10 it is collapsed forremoval.

FIG. 16 shows an alternate embodiment of a retrieval hook 170 having alonger hook 172 to increase the snare engagement area and provide a moreclosed area to retain the snare. FIGS. 18 and 19 illustrate alternativecranial ends of the filter which can be achieved using the method of thepresent invention. In FIG. 18, a rounded dome-shaped tip 210 can beengaged by a grasping device to retrieve the filter. The grasping devicecan be inserted around the curved catheter tip in the same manner asdescribed above for the snare retrieval device. In FIG. 19, a notch 222is formed in dome-shaped tip 220 to receive a retrieval snare or othergrasping device inserted through the curved retrieval catheter (sheath)tip.

To facilitate removal of the filter from the vessel, cold saline can beinjected onto the implanted filter to change the temperature of thefilter to move it to a relatively softer condition to facilitate thefilter being drawn in to the retrieval sheath. That is, injection ofcold saline will cause the filter to approach its softer martensiticstate, bringing the filter to a more flexible condition. The flexiblecondition facilitates the collapse and withdrawal of the filter into theretrieval sheath by decreasing the frictional contact between the filterand the inner surface of the retrieval sheath.

While the above description contains many specifics, those specificsshould not be construed as limitations on the scope of the disclosure,but merely as exemplifications of preferred embodiments thereof. Thoseskilled in the art will envision many other possible variations that arewithin the scope and spirit of the disclosure as defined by the claimsappended hereto.

1-20. (canceled)
 21. A vessel filter comprising a first region at acranial end and a second region at a caudal end, the filter movablebetween a collapsed position for delivery to the vessel and an expandedposition for placement within the vessel, the first region having afilter portion having a plurality of spaced apart elongated struts, aretrieval structure positioned at a cranial end of the filter, thesecond region being flared in the expanded position to have a transversedimension increasing toward the caudal end, the second region includinga plurality of vessel engaging hooks, each of the hooks having anelongated heel portion and a vessel penetrating portion, the elongatedheel portion extending further from the cranial end than the penetratingportion, in the collapsed position of the filter the elongated heelportion of one hook is nested within an adjacent hook.
 22. The vesselfilter of claim 21, wherein the second region includes a plurality ofstruts, and the plurality of struts terminate in the vessel engaginghooks.
 23. The vessel filter of claim 21, wherein the vessel engaginghooks have a curved end surface.
 24. The vessel filter of claim 22,wherein the struts of the second region have a longitudinal axis, andthe elongated heel portion extends at an angle to the longitudinal axis.25. The vessel filter of claim 21, wherein the penetrating portion has apointed tip extending in a cranial direction.
 26. The vessel filter ofclaim 21, wherein the filter is formed from a laser cut tube andcomposed of shape memory material.
 27. The vessel filter of claim 21,wherein the retrieval structure includes a hook offset from alongitudinal axis of the filter.
 28. The vessel filter of claim 21,wherein the vessel engaging hooks include a penetrating tip extending ina direction opposite to the direction the heel portion extends.
 29. Thevessel filter of claim 21, wherein the struts have an elongated portiontransitioning into a curved region and in the collapsed position theheel portion of an adjacent vessel engaging hook extends along theelongated portion.
 30. The vessel filter of claim 21, wherein the vesselengaging hooks comprises a first set of hooks and a second set of hooks,the first set of hooks terminating at a more cranial position than thesecond set of hooks.
 31. A vessel filter comprising a body made from asingle tube, the tube cut to create a plurality of elongated strutsforming a filter region and a mounting region, the mounting regionincluding a plurality of vessel engaging hooks, each of the vesselengaging hooks having a curved concave region, and a penetrating tippointing in a direction toward the filter region, and an elongated heelextending beyond the penetrating tip in a direction away from thefiltering region, the filter movable between a collapsed position fordelivery and an expanded position for placement, in the collapsedposition the elongated heel of one vessel engaging hook is closer to thecranial end of the filter than the elongated heel of an adjacent vesselengaging hook.
 32. The vessel filter of claim 31, wherein the elongatedheel of the vessel engaging hooks terminates in a curved surface. 33.The vessel filter of claim 31, wherein in the collapsed position thepenetrating tip of one vessel engaging hook overlaps the elongated heelof an adjacent vessel engaging hook.
 34. The vessel filter of claim 31,wherein the elongated heel of the vessel engaging hooks extends at anangle to the longitudinal axis of a strut which terminates in the vesselengaging hook.
 35. The vessel filter of claim 31, wherein the vesselengaging hooks comprises a first set of hooks and a second set of hooks,the first set of hooks terminating at a more cranial position than thesecond set of hooks.
 36. The vessel filter of claim 35, wherein thefirst set of vessel engaging hooks is nested within a respective vesselengaging hook of the second set of vessel engaging hooks.
 37. The vesselengaging hook of claim 31, wherein the penetrating tip of one vesselengaging hook terminates more cranial than the penetrating tip of anadjacent vessel engaging hook.
 38. The vessel engaging hook of claim 31,wherein a height dimension of a first set of hooks exceeds a heightdimension of a second set of hooks.